Over 2.7 million military personnel were deployed to Afghanistan, Iraq, and other countries in Southwest Asia and exposed to high levels of particulate matter ?2.5 m in diameter (PM2.5, particles small enough to deposit in the small airways and alveoli) from frequent dust storms, burn-pit smoke (waste burning), and poorly regulated industrial and vehicular sources. Previous studies have reported that deployed personnel have experienced symptoms consistent with chronic respiratory disease. However, objective evidence of exposure- related health effects is limited. To address this concern, VA Cooperative Study #595 ?Service and Health Among Deployed Veterans (SHADE)? is being conducted to examine the hypothesis that greater cumulative exposure to PM2.5 while deployed is associated with lower lung function assessed by spirometry. A key strength of SHADE is an exposure assessment approach that will use of historical satellite and regional visibility records to reconstruct deployment-related PM2.5 in 5000 Veterans assessed at 6 centers. A limitation of spirometry is that it is insensitive to early lung disease. This proposal is one of three collaborative projects to systematically examine the pulmonary and systemic consequences of exposure during deployment. We will conduct additional assessments in 280 SHADE participants (70 at each of four sites; Boston, Minneapolis, Seattle, Houston) with and without respiratory symptoms (cough, wheeze, dyspnea) as assessed on the CSP #595 respiratory health questionnaire and with little smoking history (former smokers with <10 pack years or never smokers). In the Boston proposal we will use CT imaging to test the hypothesis that Veterans deployed to Southwest Asia and Afghanistan will have evidence of structural lung disease associated with respiratory symptoms, a lower FEV1, and deployment-related PM2.5. In addition to structural assessment by CT scan, as part of each collaborative proposal, participants will also have (a) assessment of systemic biomarkers and immune cell activation (lead by Minneapolis and Houston VA), and (b) additional physiologic characterization using diffusion capacity (gas exchange), exhaled nitric oxide (eosinophilic airway inflammation), and IgE and eosinophilia (allergy) (lead by VA Puget Sound). We will test the hypothesis that greater exposure to deployment-related PM2.5 results in specific airway and lung parenchymal endotypes that could be distinguished by functional, structural, and biochemical mechanisms. Our three coordinated proposals will complement CSP #595 by comprehensively characterizing early deployment-related lung findings related to PM2.5 exposure that may in the future be used to assess disease. The resultant exposure-related disease types identified provide new clinical applications for the recognition, management, and future treatment strategies for Veterans with deployment-related lung disease.